Got a 3CX PBX that's registered with the VoIP provider and a Linksys SPA 922 thats registered with the PBX. If I dial in to the line registered by the PBX all I get is an unobtainable tone. If I dial out from the extension it dials the number after a long wait >10 seconds. On the extension I hear the number start to ring but this is immediately replaced by a continuous series of tones. If I register the extension directly with the VoIp provider I can make and receive calls. Thanks in advance for any help.